2007 Fiscal Year Final Research Report Summary
Temporal and Spatial Variation of Beach Cusp on Sandy Beach
| Project/Area Number |
18360240
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
水工水理学
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| Research Institution | Independent Administrative Institution Port and Airport Research Institute |
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Principal Investigator |
KURIYAMA Yoshiaki Independent Administrative Institution Port and Airport Research Institute, Marine Environment and Engineering Dep., Division Head (60344313)
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| Co-Investigator(Kenkyū-buntansha) |
YANAGISHIMA Shinichi Port and Airport Research Institute, Marine Environment and Engineering Dep., Senior Research Engineer (40392972)
SUZUKI Koujiro Port and Airport Research Institute, Marine Environment and Engineering Dep., Senior Research Engineer (50360764)
SUZUKI Takayuki Port and Airport Research Institute, Marine Environment and Engineering Dep., Research Engineer (90397084)
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| Project Period (FY) |
2006 – 2007
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| Keywords | Cusp / Sandy beach / Shoreline / Morphological change / Field measurement |
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| Research Abstract |
On sandy beaches, morphological features that are rhythmic in the alongshore direction are frequently observed near the shoreline. The objective of this study is to investigate the vertical and horizontal morphological characteristics of giant cusps on the basis of a 6-year morphological data set near the shoreline.
On the basis of the obtained morphological data, we represented contour lines at elevations between 0.2 m to 2.9 m with intervals of 0.1 m using sinusoidal curves. The correlation coefficient between the contour line position at each elevation and that at an elevation of 0.2 m averaged for 29 measurements decreased with the increase in elevation from 0.2 m to 0.5 m It was almost constant from 0.5 m to 1.4 m, and then decreased again from 1.5 m The berm crest elevations were mostly located above 1.5 m These results indicate that the cusp feature at an elevation of 0.2 m maintained vertically up to 1.5 m, which was almost equal to the lower limit of the berm crest elevation. In the area from 0.2 m to 1.5 m in elevation, the cusp amplitude averaged for 29 measurements decreased with the increase in elevation, whereas the average cusp wavelength was almost constant.
As for the development and decay of the cusp amplitude at an elevation of 0.2 m, the cusp amplitude increased with the increase in the cumulative offshore wave energy flux. The cusp wavelength was proportional to the cube of the offshore wave period.
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